There are some decent deals on GTX 460 1Gb cards to be had. I'd investigate those. If you overclock and want a cool quiet card, get that.
It's only 10usd over most regular 460 1Gb cards. I wouldn't be surprised if it could do 850 on the core with Afterburner and hold respectable thermals. TPU tested one and got 848 on the core with a load temp of 58C.